Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $58.26   6.806%   $62.2252   $62.23   $62.25   $62.20  
  Purchase #2 $47.48   3.407%   $49.0976   $49.10   $49.10   $49.10  
  Purchase #3 $107.71   10.785%   $119.3265   $119.33   $119.35   $119.30  
  Purchase #4 $151.99   5.131%   $159.7886   $159.79   $159.80   $159.80  
  Purchase #5 $15.49   8.130%   $16.7493   $16.75   $16.75   $16.70  
  Purchase #6 $119.35   5.275%   $125.6457   $125.65   $125.65   $125.60  
  Purchase #7 $222.45   5.341%   $234.3311   $234.33   $234.35   $234.30  
  7 purchase totals = $722.73       $767.1640   $767.18   $767.25   $767.00